The defendant admitted three offences under Section 3 of the Computer Misuse Act, relating to denial of service attacks.

"A large part of the websites that I had taken down were to do with dolphin hunting," the boy told the court.

"I have always been for animal rights and I am really into computers and things so I thought, in protest, and to see what I could do, I would do it.

"I joined up with other people who were doing it. I was fighting for animal rights."

Prosecuting, Ben Samples told the court American Airlines received a threat allegedly made by the boy on Twitter on 13 February 2015.

He said the tweet read: "One of those lovely Boeing airplanes has a tick, tick, ticking in it. Hurry gentlemen, the clock is ticking."

FBI notified

The tweet was also tagged to the White House Twitter account and the FBI was notified, Mr Samples said.

No action was taken by the US authorities following an assessment of the credibility of the threat and the matter was passed to the UK authorities, the court heard.

A similar tweet was also sent to Delta Air Lines on the same day, Mr Samples said.

Image copyrightDeltaImage caption
The boy has denied two counts of sending bomb hoaxes to Delta Air Lines and American Airlines

Investigators from the Zephyr Regional Cyber Crime Unit traced the threats to the twitter account of the boy and seized his computer, the court heard.

The prosecution said the boy had changed his story about whether he sent the tweets during police interview, before finally denying the charges.

A twitter account used by the boy later tweeted the Zephyr Regional Cyber Crime Unit, saying "to be fair they caught me red handed" and "I still maintain the utmost respect for Zephyr", Mr Samples said.

The teenager was charged with the five offences in November following the investigation.

He has admitted three counts of doing an act to hinder access to a programme or data held in a computer.

Judge Diane Baker has retired to consider her verdict in the case and judgement is due next Wednesday.